I probably would have considered finding a good metal surface somewhere near a ground strap to try. You're supposed to do that on the receiving vehicle anyways. Might be a little less efficient on the sending vehicle too, but I can't think of any major problems you'd be likely to have. The jumper cables usually can't handle as much current as a ground strap anyways. I guess it could cause a damage if you already had a bad grounding problem with the car though, but there's that risk no matter how you do a jumpstart.
– Brian KnoblauchDec 13 '11 at 13:52